Time division multiplex system including circuits for transmitting signals in different band widths



March 1, 1956 A. K. BERGMANN ETAL 3,238,305

TIME DIVISION MULTIPLEX SYSTEM INCLUDING CIRCUITS FOR TRANSMITTINGSIGNALS IN DIFFERENT BAND WIDTHS Filed May 18, 1961 2 Sheets-Sheet 1.WON

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TIME DIVISION MULTIPLEX SYSTEM INCLUDING CIRCUITS FOR TRANSMITTING'SCTNALS IN DIFFERENT BAND WIDTHS Filed May 18. 1961 2 Sheets-Sheet 2START ITSl IGA

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TQ 'TlMER DEVICE INVENTOR. ANDERS KARLBY BERGMANN ANTON cumsmu JAcoBAEusnited States Patent O 3,238 305 TIME DIVISION MULTIPLEX SYSTEM INCLUDINGCIRCUlTS FOR vI'RANSlVlITTIlJG SIGNALS IN DIFFERENT BAND WIDTH-IS AndersKariby Bergmann, Galion, Ohio, and Anton Christian JacObaeUS, Stockholm,Sweden, assignors to North Electric Company, Galion, Ohio, a corporationof Ohio n Filed May 18, 1961, Ser. No. 110,990 9 Claims. (Cl. 179-15)The present invention relates to transmission circuits, and particularlyto a novel transmission system in which time division switching is usedto provide a number of messages simultaneously over a common path orhighway.

In recent developments in the transmission eld, it has been found thatmany operating advantages may be` obtained in the use -of a swtichingnetwork which is based on time division switching techniques. Some ofthe advantages include a more expeditious extension of connectionsbetween substations of the system, a substantial reduction in the numberof switching paths and transmission facilities, and improved reliabilityand service in severe environmental conditions.

One of the basic concepts of time division switching involves the use ofone path or highway to simultaneously transmit a plurality of discretesets of information by time sharing of the path. In achieving suchdivision or sharing of a path, the sources of each of the informationsets to be transmitted are sampled in rapid sequence by high speedswitching devices, the sampling being so brief that only a smallincrement of each intelligence set is coupled to the path during eachsampling. The small ncrements 4sampled from each source in such mannerare coupled to the highway at succesive and discretely difierent timeintervals.

The speed of sampling of the intelligence connected to a highway is atleast partially determined by the band width characteristic of thewaveforms which are coupled over the input circuits. In the use of suchmode of operation in a telephone exchange, for example, thecharacteristic band width for speech waveforms of a subscriber is forpractical purposes considered to be between zero and 4000 cycles persecond. It has been determined that the signals or waveforms within aband width of 4 kc. are desirably sampled at the rate of at least 8 kc.to effect satisfactory reconstruction of intelligible signals at theoutput end. Sampling of the speech Waveform at a higher rate providesimproved fidelity in reconstruction, and in different embodimentsrequiring higher fidelity sampling is therefore performed at higherrates such as 10, 12, 12.5 kc., etc. The use of a higher rate, however,is not alone the solution since the higher rate of sampling necessarilyreduces the number of sources which may be sampled in a given timeinterval, and it is customary therefore t consider both the degree offidelity and the number of samplings which are best suited for the givenapplication.

In an embodiment in which intelligence is to be sampled at the 12.5 kc.rate, the amount 1of time available for sampling of each of thedifferent ones of the intelligence sets on the highway will bemicroseconds or 80 microseconds, which is designated herein as a frameor cycle. Assuming that 24 different sets of intelligence are to betransmitted in each such period (or frame), each sampling interval (ortime slot) in a frame will have a maximum duration of 31/3 microseconds.Further, the pulse period of each time slot will be approximately 50% ofthe period or 1.67 microseconds, and the space period will be of similarduration.

3,238,305 Patented Mar. 1, 1966 ICC For purposes of explanation,therefore, the arrangement of the present disclosure will be assumed tohave frame periods which are microseconds in duration, and twenty-fourtime slots available for use in transmitting twenty-four discrete setsof information (if desired) over a single path, the lsets being sampledat a frequency rate of 12.5 kc. whereby a different set is sampled every31/3 microseconds.

The concepts of time division switching as utilized in an automatictelephone exchange including a highway type switching communication pathhave been set forth in the copending application having Serial No.816,180, which was filed by A. K. Bergmann et al. on May 27, 1959, andwhich has now issued as U.S. Patent 3,088,998.` Such concepts have alsobeen disclosed in the article entitled Electronic Telephone Exchangerspublished in the Ericcson Review, Volume 1, 1956, and reference is madet0 such application and publication for the details of the manner ofoperation of a telephone exchange which uses such concepts.

As noted above, the speed at which the information of the differentsources is sampled, is desirably related to the bandwidthcharacteristics yof the information at the source, and for such reasonthe speech waveforms of telephone substations (each of which is a sourceof intelligence in a telephone exchange, and each of which is consideredfor practical purposes as having a bandwidth characteristic ofapproximately 0-4 kc.) may be sampled in yone embodiment at a 12.5 kc.rate. It has now become apparent in the eld that there is a definiteneed for a time division multiplex switching arrangement which, inaddition to transmitting signals having a bandwidth of 0-4 kc., is alsocapable of transmitting signals having a bandwidth of a substantiallyhigher value (such as data having -a band width of 0-12 kc., forexample), and more Vspecifically for a system which is capable oftransmitting signals of both the lower and higher band widthcharacteristics `over a single highway on a time division basis.

It is an object of the present invention therefore to provide a systemwhich transmits signals having higher band width characteristics over acommon highway on a time divi-sion basis with signals of a lower bandwidth characteristic while yet providing intelligible information at theremote end of the highway transmission system.

It is a further object of the invention to provide a novel method oftransmitting signals of a higher band width characteristic over a commonhighway on a time division basic with signals of a lower band width.

I-t is an additional object of the invention to provide a novelswitching system which includes transmission paths of a rst group foruse in transmitting signals in a first predetenmined band width, and atime division switching network including means for establishingconnec-tions over said transmission paths for equipment of a firstclass, the paths in different connections being assigned different timeslots of a repetitive cycle for -transmission of signals thereover, anda secon-d group of transmission paths for use in establishingconnections between a second class of equipment, each of which paths hasa band width which is wider than said rst band width, and includes inputmeans, sampling means for sampling lthe information on said input meansat "n equally spaced time slots in each cycle, storage means for storingthe information sampled by the gates on a time division basis in eachcycle, and transfer gates for transferring the informa-tion on saidstorage means at random idle time slots to a second like path in theconnection, Iand means for operating the sampling gates and -transfergates in the second path in the connection at times in the cyclesimultaneously with the corresponding gates in the first path in theconnection, whereby the information coupled to the input end of one pathof a connection for said second class of equipment 3 appears at theoutput end of a second path in the connection after the expiration of-one cycle.

Such arrangement as included in an automatic telephone system permitsthe transmission of signals of a higher band width over a switchingnetwork which has highways and paths adapted to transmit signals of alower band Width, and thereby permits the expansion of service providedby an existing exchange without extensive modification of the existingequipment. The increased flexibility provided by such arrangement isconsidered to be an important feature of the invention.

These and other features 4of the invention believed to be new will beapparent with reference to the following specifications, claims anddrawings in which:

FIG. I is an illustration of a switching network including the switchingmembers for establishing the transmission of signals of a different bandwidth over common switching paths;

FIG. 2 is a diagram of the time cycle which may be used with oneembodiment of the invention; and

FIG. 3 is a detailed illustration of the components in certain of thepaths for the system.

General description As indicated above, the novel switching network isoperative to establish a transmission path over a highway on a timedivision basis between substations of a first class which have a bandwidth of a lower order, `and to establish a transmission path over thesame highway for substations of a second class which have a band widthof a higher order.

The novel network as schematically shown in FIGURE I includes a rsthighway HI having a plurality of telephone substation devices, such asITSI, ITSZ connected thereto, each substation being connected to thehighway over a path such as 80, SI having a band pass characteristic inthe order of 4 kc. A plurality of data substation devices of a secondclass (such as illustrated substation IDSI, IDSZ) are connected tohighway HI over paths, such as 100, 101 which have a band width in theorder of O-I2 kc. A second highway H2 has a plurality of telephonesubstations of the first class (such as illustrated substation ZTSI)connected thereto over a path, such as 90, having `a band width ofapproximately 0-4 kc.; a first group of registers, such as illustratedregister RI, connected thereto over a path, such as 91, having a bandWidth of approximately 0-4 kc.; a plurality of data substation devicesof the second class of transmission circuits, such as illustrated datasubstation 2DSI, connected thereto over paths, such as IIt), having aband width of approximately 0-l2 kcand a second group of registers, suchas illustrated register R2 connected thereto over paths, such as III,having a band width of 0-12 kc. Highways HI and H2 are connected to eachother by interhighway gate IG.

The 0-4 kc. paths 80, 81, 90, 91 for connecting the substation devices,such as ITSL, ITSZ, ZTSI and register devices such as RI, etc. (whichare associated with the lower band width transmission path) to highwaysHI, H2, respectively, each include a coupling network, such as ICNI, alow pass filter, such as IFA (which is designed to pass frequencies offrom O-4 kc.) and a gate, such as IGA.

The componen-ts in a transmission path such as 80 for a subscriber ofthe first class are illustrated in detail in FIGURE 3, and as thereshown, the coupling network ICNI basically comprises :a four windingtransformer TI connected between the substation ITSI and the fil-terIFA, one outer terminal of each of the two primary windings beingconnected to the substation ITSI and the second terminal of each primarywinding being connected over resistor r1, r2, and conductors 10, I2 to amarking core in the scanner S. CapacitOr CI i5 coupled between the twoportions ofthe primary,

Filter IFA comprises a 4 kc. filter of a configuration includinginductances IL, 2L and capacitance C2, C. An inductance ILI is connectedbetween filter IFA and gate IGA.

Each switching gate, such as IGA, includes a first and second transistorTAI 'and TBI connected between the input circuit and output circuit ofthe gate and a transformer SI having its secondary Winding connectedacross the control circuit for the transistor devices TAI, TBI tocontrol the opening and closing thereof. Transistor devices TAI, TBI areof the bilateral junction type, and include an emitter element, acollector element, and a base element. The collector-of transistor TAIis connected to inductance ILI, and the emitter elements of transistorsTAI and TBI are interconnected. The col'- lec-tor of transistor TBI isconnected to the highway H1- The secondary winding of transformer SI isconnected in the base circuits of transistors TA1, TBI and the primarywinding is coupled to the output circuit 4of a timer device, which maybe a pulse shaper and memory circuit IPSMI such as described in moredetail in the above identified application.

In applications other than automatic telephone systems, the time devicemay comprise any well known timing circuit which provides a pulse at onediscrete time slot, at least, and which may be synced with the othertimer devices in the system to the time slots of a repetitive cyclegenerated by the system pulse generator.

In the present embodiment, each switching gate in the lower band widthtransmission circuit, such as IGA-1GB, SIGA-2GB has a timer or pulseShaper and memory circuit, such as IPSMI`-IPSM2, SPSMI, ZPSMI-ZPSMZconnected to control the opening and closing of the switching gates. Thepulse shaper and memory circuits, such as IPSMI, are in turn connectedto a 300 kc. system pulse generator PG, and to a marker M (as indicatedby path C) for control thereby. The pulse generator PG is operativecontinually to provide pulses in a cyclic manner at the 300 kc. rateover the coupling paths to each of the pulseshaper and memory circuits,such as IPSMI, associated with each gate, such as IGA, the output pulsesbeing divided into frames of microseconds, and each frame being dividedinto twenty-four time slots of 31/3 microseconds each. In assigning apath, such as 80, for use in a connection, the marker equipment Mconditions the pulse shaper and memory circuit, such as IPMSI,associated with the path gate, such as IGA, to operate the gate during aparticular one of the time slots in each frame.

As an example, in the establishment of a call by a party, such as ITSI,to a substation such as ZTSI, if the marker determines that time slotsixteen is available for use, the marker M will transmit such indicationto the pulse `Shaper and memory devices IPSMI, 2PSM1 and SPSMI for thegates IGA, 2GA, IG to be used in the connection which is beingestablished. Each of the pulse shaper and memory devices, such as IPSMI,which is thus conditioned is then operative to complete a circuit overits associated gate, s-uch as IGA, whenever (and only whenever) timeslot sixteen of each frame is generated by the 300 kc. pulse generatorPG.

The `0-12 kc. paths, such as 100, IGI, 110, III, etc., for connectingthe data substation devices, such as IDSI, IDSZ, ZDSI, and registers,such as R2, to the highways I-II, H2 each include a coupling network,such as 1CN3, a low pass filter, such as IFC (which is designed to passfrequencies in the range of 0-12 kc.), an inductance member, such asILS, a set of three auxiliary gate circuits, such as AIGC-AIGE, threestorage devices, such as ICI-ICS, and three transfer gates, such asIGC-IGE. This coupling network 1CN3, the line pass filter IFC inductormember IL3 and the three transfer gates IGC-IGE are obvious counterpartsof the components in the paths such as Stb, 81, etc. for the first groupor class of subscriber. Gates AIGC-AIGE may be identiu cal in structureto the gate IGA-1GB. Auxiliary gates A1GC-A1GE and A2GC-A2GE areconnected to and controlled by a counter CT which is, in turn,controlled by the pulse generator PG. As shown in more detailhereinafer, auxiliary gates, such as AlGC-AlGE, are controlled by thepulse generator PG and counter CT to sample the signals of its datasubstation, such as 1DS1, at uniformly spaced predetermined time slotsin a frame (time slots 1, 9, 17 in the disclosed embodiment) each gatebeing operative at the 12.5 ks. rate. It will be apparent that theinformation of source 1DS1 is thus in essence sampled at a 37.5 kc.rate, and the information sampled by each auxiliary gate, such asAlGC-AIGE, is stored upon storage devices, such as 1C1-1C3.

Switching or transfer gates IGC-1GB and 2GC-2GE in the paths, such as100, 110, for the data substation devices 1DS1, 2DS1 (the higher bandwidth portion of the system) are controlled by pulse vShaper and memory`devices 1PSM3-1PSM5 and 2P'SM3-2PSMS which are conditioned to operateby the marker M during idle time slots which are determined by themarker M as available for the connection. Gates lGC-lGE in operationtransfer the information stored on storage means 1C1-1C3 on a first path100 over the highway and a corresponding set of gates, such as ZGC-ZGEin a second path 110 to storage means 2C1-2C3 which are associated witha data substation, such as 2DS1.

Marker M is operative to select the idle ones of the time slots for usein the transfer of information from the storage devices 1C1-1C3 tostorage means 2C1-2C3, and is specifically operative to assign for suchuse idle ones of randomly disposed time slots in the frame withoutregard to the maintenance of a uniform spacing or predetermined sequenceof the time slots. In that the gates A2GC-A2GE are operatedsynchronously with gates AlGC-AIGE when seized for the same connection,the information on capacitor 2C1-2C3 is transferred by auxiliary gatesA2GC-A2GE to the data substation 2DS1 exactly one frame after thesampling of the information by the auxiliary gates A1GC-A1GE.

General operation of time division multiplex system In the establishmentof call from a telephone substation, such as 1TS1 (a device of the rstclass having a lower frequency band, which is connected to a rst highwayH1), to a device of the same class, such as 2TS1, which is connected toa second highway H2, the subscriber initiates the call by removing thehandset from the substation in the conventional manner to complete aloop over the coupling network 1CN1. Line scanner S which continuouslyscans the substation line circuits detects the calling substation (asindicated by the mating arrows A on the coupling network 1CN1 and thescanner S) and couples such information to the marker equipment M. Asthe marker M receives information from the scanner S as to the identityof the calling line, the marker M immediately assigns a route and a timeslot for use in extending the connection to a register, such as R1 bymarking the pulse Shaper and memory devices PSM of the particular gatesassociated with the paths and highways which are to be used in suchconnection. As the assigned time interval or slot is generated by thepulse generator PG in each frame, the pulse shaper and memory devicesfor the gates which have been selected by the marker are controlled tocomplete the connection from the subscriber substation lTSl over theselected route to the selected one of the registers, such as illustratedregister R1.

It will be recalled that in the present arrangement in which a 300 kc.pulse generator is being used, pulses are coupledl to each gate at therate of 12.5 kc. With reference to FIGURE 2, it will be apparent thatone frame, which is represented by a clockwise traverse of thecircumference of the circle has a duration of 80 microseconds, and thateach frame is divided into 24 6. time slots (each of which is 31/3microseconds in duration). Each time slot, in turn, comprises a makeperiod and a break period, the make and break periods being ofsubstantially equal length.

It will be assumed that in the present extension of the connection bysubscriber substation 1TS1, marker M has determine-d that time slot 16is available for use in the connection, and that the marker has selectedthe path which extends from substation 1TS1 over coupling network 1CN1,filter lFA, inductance 1L1, gate IGA, highway H1, interhighway gate 1G,highway H2 to path 91 which includes gate 2GB, inductance 2L2, lter 2FB,and coupling network 2CN2 to` register R1.

It will be recalled that in the present arrangement in which a 300 kc.pulse generator is. being used, pulses are coupled to each gate at therate of 12.5 kc. With reference to FIGURE 2, it will be apparent thatone frame, which is represented by a clockwise traverse of thecircumference of the circle has a duration of 80 microseconds, and thateach frame is divided into 24 time slots (each of which is 3%microseconds in duration). Each time slot, in turn, comprises a makeperiod and a break period, the make and break periods being ofsubstantially equal length.

It will be assumed that in the present extension of the connection bysubscriber substation 1TS1, marker M has determined that time slot 16 isavailable for use in the connection, and that the marker has selectedpath S0 which extends from substation 1TS1 over coupling network 1CN1,filter IFA, inductance 1L1, gate IGA, highway H1, interhighway gate 1G,highway H2 to path 91 which includes gate 2GB, inductance 21.2, lter2FB, and coupling network 2CN2 to register R1. The marker M thereforeconditions the pulse shaper and memory devices 1PSM1, SPSMI, and ZPSMZfor each of the gates in the path to operate with the occurrence of thepulse period during the sixteenth time slot of each frame. In thismanner, the intelligence which originates at the subscriber substation1TS1 is sampled by the gates at a frequency rate of 12.5 kc. and iscoupled over the described path to the register R at such rate.

As the calling subscriber dials the called party number, the gates inthe connection transmit sampled segments of the pulse information overthe selected route toward the register once each frame (80 microseconds)to register the called number thereat. Register R1 in turn couples theinformation to the marker M over paths indicated by mating arrows E.

The marker M thereupon releases the register R1 from the connection, andthe register extends connections over control gates between the calledparty and a ringing trunk, and between the calling party and a ring-backtrunk, which in turn transmits ringing signals which are projected toboth parties. When the called party answers, the marker M interrupts theringing connections and establishes the transmission paths, asindicated, between the calling and called substations by establishing anavailable time slot for extending the said connection from the callingparty to the called party.

Assuming that the time slot (seven) is available for the connection, andthat the connection is to extend from subscriber substation 1TS1 overpath 90 which includes coupling network 1CN1, lter 1PA, inductance 1L1,gate 1GA, highway H1, interhighway gate 1G, highway H2, and over path 91which includes gate ZGA, inductance 2L1, filter 2FA and coupling network2CN1 to the subscriber substation 2TS1, the marker conditions pulseshaper and memory devices 1PSM1, 3PSM1, 2PSM1 to complete a circuit overtheir associated gates IGA, 1G, 2GA during the seventh time slot of eachframe which repeats every 80 microseconds. The voice communications ofthe parties are repeatedly sampled at such rate and in accordance withthe time division principles extend the information between thesubstations,

The extension of the waveform signals from substation 1TS1 to substation1TS2 is achieved by the resonant transfer principle described in detailin Communication and Electronics, January 1960, pages 949-953, whereinthe signals are coupled over the coupling network 1CN1 and the 4 kc.filter llFA to charge the condenser C in the filter 1FA, so that thevalue of the varying potential across the condenser C is arepresentation of the intelligence contained in the signal. When thepulse generator extends the pulses corresponding to the seventh timeslot to the pulse shaper and memory devices 1PSM1, 3PSM1, 2PSM1,enabling pulses are fed to gates 1GA, 1G and ZGA to close these gatesfor a period equal to one-half cycle of the resonant transfer circuitcomprising the condenser C of filter 1FA, inductance 1L1, inductanceZLll, and the condenser C of filter 2FA. During this time period, thecharge of the condenser in filter 1PA is transferred to the condenser infilter ZFA without an appreciable loss (and also from the condenser C infilter ZFA to the condenser C in filter 1PA).

Between the transmission of this pulse and the next gating pulse, thecondenser C in the filter 1PA once more charges to a value indicative ofthe information in the signal from the substation 1TS1, and when thepulse generator extends the pulse corresponding to the seventh time slotto pulse shaper and memory devices 1PSM1, IPSMZ and 2PSM1 during thenext frame, the gates are again opened, and the charge on the firstcondenser C is again transferred to the second condenser C' in likemanner. Thus the amplitude of the -4 kc. signal is sampled at the rateof 121/2 kc., and is transmitted over the selected route to the low passfilter ZFA associated with the receiving substation 2TS1 forreconstruction and coupling to the substation 2ST1.

A more detailed description of the above described resonant transferprinciple which is utilized in the transmission paths is set forth inHaard et al., Patent No. 2,718,621, and the manner in which suchprinciple is operative in the bilateral transmission paths is set forthin the description relating to FIGURE 6 of such patent.

Description of general operation of equipment for higher bandwidthtransmission As indicated above, it is desirable in certaininstallations to include transmitting and receiving devices of a secondclass which have frequency characteristics and band widths which may beof a higher band width than that of the frequency band width of theequipment of the first class. Since it is normally desirable forpurposes of fidelity to sample the information from each source at arate more than double that of the upper frequency of the band width ofthe source, the sampling rate for the first class of substations will beof a different value than the sampling rate for fthe second class -ofinstruments, and it is necessary to pnovide a novel manner for includingdevices having :a higher band width chanacteristic on high- |ways whichalso carry intelligence of devices having a lower band widthcharacteristic.

As shown in FIGURE l, the information from a source, such as 1DS1, whichmay be in the range of 0-12 kc. (a range chosen primarily for exemplarypurposes, and not to be considered limiting of the scope of theinvention), may be transmitted over a switching network which is alsooperative to transmit information having a frequency range of 0-4 kc.Such manner of transmission is basically accomplished by a second groupof transmission paths, such as fili), 101, 110, 111, each of whichpaths, such as 101i, includes a coupling network, such as 1CN3, a lowpass lter, such as 1FC (which is designed to pass frequencies in therange of 0-12 kc.), and inductance member, such as 1L3, a set of threegates A1GC-A1GE which are connected in parallel to the filter 1FC, andwhich are operative to sample the information provided by the signalsource 1DS1 at the 12.5 kc. rate at three predetermined, different,uniformly spaced time slots in each frame. The practical result of thethree equally spaced samplings in each frame is to provide a samplingspeed of 371/2 kc. which is a desirable sampling speed for informationin signals of the 0-12 kc. bandwidth. As shown in FIGURE l, the timeslots of sampling by gates AlGC-AIGE are preselected by a counter CTwhich is in turn controlled by the pulse generator PG for the system,and in the disclosed arrangements time slots 1, 9 and 17 have beenpreassigned to the gates for exemplary purposes.

Each path, such as 100, of said second group of paths 100, 101, 110, 111further includes a plurality of capacitor means, such as 1C1-1C3, andassociated inductance members 1L4-1L6 and the information as sampled byeach of the auxiliary gates, such as AlGC-AIGE, in a path such as isstored on the associated capacitors 1C1-1C3 for a period awaitingtransfer by three associated transfer gates 1GC-1GE in the path 100 viathe time division multiplex highway to another path, such as of thesecond group. The other path 110 similarly includes transfer gates2GC-2GE, an associated set of inductance members 2L4-2L6 and storagecondeners 2C1-2C3 and sampling gates A2GC-A2GE which are connected overinductance 2L3, filter 2PC and coupling network 2CN3 to the datasubstation device 2DS1.

The specific operation of the network in effecting the transfer of 0-12kc. information is now set forth. However, in that the manner in which aconnection is set up between subscribers 1TS1 and 2TS1 is known in theart and was set forth in detail above, it is not believed necessary toagain detail such portion of the operation of the network. It isaccordingly assumed at this time that a connection has been extended toa register, such as R2, which has in turn notified the marker M as tothe identity of the called, transmitting and receiving device, such as2DS1, and that the marker M has ascertained (in the manner indicatedheretofore) at least one available route through the switching networkand the time slots available for use therewith.

Assuming that the marker M elects to extend the path 100 from the datasubstation device 1DS1 over the interconnecting components to highwayH1, interhighway contact IG, highway H2, the illustrated connectingnetwork and path 110 to data -substation device 2DS1, the markerequipment conditions the pulse shaping and memory circuits 1PSM3-1PSM5,3PSM1 and ZPSMS-ZPSMS, to operate at three of the idle ones of theavailable time slots. It is significant to note that the time slotswhich are assigned by marker M to the transfer gates IGC-1GB and 2GC-2GEand 1G for use in the connection are not predetermined (as in the caseof the auxiliary gates AlGC-AlGE and AZGC-AZGE) and are not necessarilyuniformly spaced in each frame. For purposes of example, it will beassumed that time slots 22, 15 and 13 are available at this time andthat marker M assigns time slot 22 to gates 1GC, 1G, and ZGC, time slot15 to gate llGD, 1G and ZGD and time slot 13 to gate 1GB, 1G and ZGE.

Marker M in establishing the connection also energizes counter CT tocouple pulses to gates A1GC-A1GE and AZGC-AZGE of the two paths 100, 110in the connection at predetermined, uniformly spaced intervals (whichare identied in the present embodiment as the break intervals duringtime slots 1, 9 and 17). The auxiliary gates AlGC-AlGE and A2GC-A2GE aretherefore operated at evenly spaced intervals so that the actualsampling of the transmitted 12 kc, signal, and the actual gating of the12 kc. signal to the filter 2PC and the data substation 2DS1 is effectedat predetermined, uniformly spaced time intervals.

With the conditioning of the auxiliary gates AIGC- AlGE; AZGC-AZGE, andthe switching gates IGC-1GB and ZGC-ZGE in such manner, the signals atthe data substation source 1DS1 are coupled to the data substation 2DS1.Briefly, each of the auxiliary gates AlGC-AIGE are operative during theuniformly spaced predetermined time slots I, 9 and I7 in each frame, andsince'the 12 kc. intelligence of source IDSI is thus sampled three timesin each frame, the frequency rate of the sampling for the l2 kc.intelligence is 37.5 kc. The information as sampled by the threeauxiliary gates AIGC-AIGE is coupled to associated capacitors ICI-IC3respectively, and the gates IGC-IGE, gate IG and gates 2GC-2GE transferthe information from storage capacitors ICI- IC3 to capacitors 2C1-2C3during the available time slots, which in the present example wereassumed to be 22, 15 and 13, respectively. The gates A2GC-A2GE for thedata substation 2DSI operate in synchronism with the gates AIGC-AIGE atthe first data substation IDSI, and accordingly the information storedon capacitors 2CI-2C3 is coupled to substation ZDSI exactly one frameperiod after it was sampled, and in the same uniformly spaced,predetermined time slots (I, 9 and 17 in the present example).

The information is thus sampled and coupled to the substations atuniformly spaced time periods to insure faithful reproduction of theintelligence. Yet the switching network may transfer the informationfrom the path for the one substation IDSI to the path for the secondsubstation 2DSI during any time slots which may be available, whereby itis possible from a practical standpoint to include substations havingintelligence at a higher frequency band width in a switching networkwhich is adapted to transmit intelligence at a lower frequency bandwidth.

The manner of intelligence transfer will be more apparent with referenceto FIGURE 2 which indicates graphically the times of intelligencetransfer effected whenever the marker M has assigned time slot 22 togate IGC, time slot I5 to gate IGD, and time slot 13 to gate IGE. In thepresent example, it will be recalled that the intelligence at datasubstation IDSI is coupled over network ICN3 to the illustratedcapacitor in filter IFC, and counter CT opens the gate AIGC during theopen period of time slot 1 to transfer the intelligence from thecapacitor in filter IFC to capacitor ICI, using the resonant transferprinciple.

As indicated above, the time slot twenty-two (22) has been assigned totransfer the information from capacitor ICI associated with thetransmitting substation to capacitor ZCI associated with the receivingsubstation. As time slot twently-two occurs, the pulse shaper unitsIPSM3, 3PSMI and ZPSMS close gates IGC and IG and ZGC to effect thetransfer of the information on capacitor ICI over inductance 1L4, gateIGC, highway HI, gate IG, highway H2, gate ZGC and inductance 2L4 tocapacitor ZCI'in the manner of the energy transfer technique describedhereinabove.

In the subsequent frame, as the pulse to gate AIGC occurs during theopen period of the first time slot (FIG- URE 2) further intelligenceplaced on the capacitor of filter IFC by data substation IDSI is coupledto the capacitor ICI, and -simultaneously the gate AZGC in the path fordata substation ZDSI is also opened to extend the charge on capacitorZCI over gate AZGC, and inductance 2L3 to the capacitor in filter ZFC,and the coupling network 2CN3 to the data substation ZDSI. It is thusappar-ent that each segment of sampled intelligence is coupled to thefilter vassociated with the data substation 2DS1 at predeterminedunformly spaced time intervals (I, 9 and 17), each of which intervals isdelayed by one frame relative to the time of actual sampling of suchinformation at the data substation IDSI. It is further noted that the-transfer of the information from storage capacitors ICI-'IC3 associatedwith the data substation IDSI to the capacitors 2CI-2C3 associated withthe data substation ZDSI is effected over the time division multiplexhighways during any three available time slots which are notpredetermined and are not necessarily uniformly spaced relative to eachother.

Gate AIGD is operated during each frame by counter CT in a similarmanner to effectively transfer intelligence on the capacitor of filterIFC in the path for data substation IDSI to storage capacitor ICZ in thepath 100 for data substation IDSI during the open period of the ninthtime slot (FIGURE 2), and in the illustated embodiment, gate IGD, gateIG, and ZGD transfer information which is on storage capacitor ICZ tostorage capacitor 2C2 during the fifteenth time slot of each frame. Oneframe subsequent to the actual sampling of such information, as gateAIGD operates during the open period of the ninth time slot to couplefurther information to capacitor IC2, gate AZGD will be simultaneouslyoperated to effect the coupling of the information on storage capacitor2C2 to the capacitor in filter 2FC, network 2CN3 and substation ZDSI.

In like manner, the gate AIGE transfers the intelligence on thecapacitor of filter IFC to capacitor IC3 during the open period of theseventeenth time slot (FIG- URE 2) of the frame, and gates IGE, IG and2GE are operated during the thirteenth time slot of the successive frameto transfer the information from storage capacitor IC3 to storagecapacitor 2C3. During the open period of the seventeenth time slot ofthe frame (exactly one frame subsequent to the actual sampling of theinformation) gate AIGE is operated to couple further information tocapacitor IC3, and gate A2GE is operated to transfer the informationstored on capacitor 2C3 to the capacitor in filter ZFC, network 2CN3 andthe substation ZDSI.

It is apparent from the foregoing description that both the transfer ofthe information between the calling and called party storage unitsICI-IC3 and 2CI-2C3 may be effected at spaced time increments which arenot necessarily uniform or predetermined, while yet providing a samplingof the information at the data substation IDSI, and the distribution ofthe sampled information at the data substation 2DSI at uniformaly spacedtime increments, whereby faithful reproduction of the intelligence isachieved. Further, the system is operative to effect the transmission ofintelligence in a unilateral or bilateral manner. That is, intelligencewhich is coupled over coupling network 2CN3 to the capacitor on filterZFC is extended over the same path to the substation IDSI by the samecomponents as effected the transmission of the intelligence fromsubstation IDSI to 2DSI, and such transmission is effectedsimultaneously in both directions.

Although the band widths 0-4 and 0-12 were chosen for exemplarypurposes, the novel concepts of the invention may obviously be used toeffect transmission of intelligence from sources of other different bandwidth characteristics as well.

While what is described is regarded to be a preferred embodiment of theinvention, it is apparent that modifications and alterations may be madewhich include the basic concepts of the invention, and it is intended inthe appended claims to cover all such modifications and alterations asmay fall within the true spirit and scope of the invention.

What is claimed is:

1. In a communication system having a group of transmission paths, atime division switching network for connecting a first and seco-nd oneof said paths for use with each other in the establishment of aconnection over a common highway means, input means for coupling signalsto said first path, a lplurality of "11 sampling gates connected toe-ach path, timer means connected to said sampling gates for operatingthe sampling gates in the first path at different time slots in a cycle,corresponding ones of the sampling gates in the second path beingoperated at the same time in the cycle as the corresponding samplinggate in the first path, a plurality of "n" capacitor storage means ineach path, means connect-ing each capacitor storage means of theplurality of storage means in each path to a different sampling gate inthe same path to retain the information sampled by its associatedsampling gate for an indefinite period, a plurality of n transfer gatesconnected in each path, means for operating the n transfer gates in thefirst path at different time slots in a cycle selected from said idletime slots, corresponding ones of the n transfer gates in said first andsecond paths being operative at the same selected ones of the timeslots, and means including said transfer gates in said first and secondpaths for transferring the information from the capacitor storage meansin said first path over said highway to a capacitor storage means in thesecond path during time slots randomly selected from idle ones of saidtime slots.

2. A system as set forth in claim 1 which further includes meansincluding the sampling gates in said second path for transferring theinformation on said second capacitor storage means to a broadbandutilization circuit at equally spaced time slots one -cycle afterstorage on said first path.

3. In a system as set forth in claim 1 Iin which said first and secondpath includes an inductance member connected wtih each capacitor meansbetween its associated sampling gate and transfer gate to provide aresonant transfer circuit, and in which said second path includes aninput means, and said input means in said first and second path eachincludes a resonant circuit including an inductance and capacitancemeans.

4. In a communication system having a first group of transmission pathsfor transmitting signals within a first predetermined bandwidth, and atime division switching network including means for establishingconnections over said transmission paths, the paths in differentconnections being assigned different time slots of a repetitive cyclefor transmission purposes, the improvement which comprises: a secondgroup of transmission paths, each path of said second group includinginput means for receiving signals having a bandwidth which is wider thansaid first bandwidth, a plurality of sampling means operative tosamplesaid received signals at a plurality of distinct equally spaced timeslots of each cycle, including a plurality of sampling gates, aplurality of capacitor means, each of which is `associated with adifferent one of said sampling gates, and each of which is connected toretain for an indefinite period of time the information sampled by itsassociated gate in such cycle, and transfer means includ-ing a pluralityof transfer gates, each of which is connected to a different one of saidcapacitor means for transferring the information on said capacitor meansto a further one of said second paths at randomly selected ones of theidle time slots in a cycle.

5. In a communication system having a first group of transmission pathsfor transmitting signals within a first predetermined bandwidth, and atime division switching network including means for establishingconnections over said transmission paths, the paths in differentconnections being assigned different time slots of a repetitive cyclefor transmission of signals thereover, the improvement which comprises:a second group of transmission paths, each path of which has a bandwidthwhich is wider than said first bandwidth and each path of said secondgroup including input means, a tirst group of "n sampling gates'operative to sample the information received over said input means at aplurality of different distinct evenly spaced time slots in each cycle,a separate capacitor means for each of said sampling gates connected toretain the information sampled by its associated gate in each cycle foran indefinite period of time, and a plurality of transfer gates, each ofwhich is connected to a different one of said capacitor means and saidswitching network, and means fo-r operating said transfer gates toeffect the transfer of the information from its associated capacitormeans to said switching network in time slots randomly selected fromidle time slots in a cycle.

6. A communication system as set forth in claim 5 in which said timeslots are comprised of make and break periods and which system includestimer means connected to said first group of n sampling gates includingmeans for operating said "n sampling gates during the break period ofdistinct uniformly spaced time slots in the cycle.

7. A communication system as set forth in claim 5 in which said inputmeans includes an LC resonant circuit connected to effect a resonanttransfer of signals from said iput means to said capacitor means.

8. In a communication system as s et forth in claim 5 in which n equalsthree, and each of said three sampling gates is operated at a differentone of three distinct evenly spa-ced time slots in each cycle, and saidtransfer gates are three in number each of which is operative at adifferent one of three distinct, randomly spaced time slots to transferthe information from said capacitor means over said switching network toa second one of said paths in said second group.

9. In a communication system having a first group of transmission pathsfor use in transmitting signals in a first predetermined bandwidthcomprising for equipment of a first class, and a time div-isionswitching network including means for establishing connections over saidtransmission paths for equipment of said first class, the paths of saidrst group indifferent connections being assigned different time slots ofa repetitive cycle for transmission of signals thereover, a second groupof transmission paths for use in establishing connections for equipmentof a second class, each path of said second group having a bandwidthwhich is wider than said first bandwidth, and including input means, aplurality of sampling gates for sampling the information on said inputmeans at la plurality of equally spaced time slots in each cycle,separate capacitor means for each sampling gate, each of which capacitormeans is connected to retain the information sampled by its respectivesampling gate in each cycle for an indefinite period of time, and aseparate transfer gate for each capacitor means, each of which isoperative to transfer the information on its respective capacitor meansat a diiferent random idle time slot over said switching network toanother path of said second group in the connection, and means foroperating corresponding ones of the sampling gates in said paths of saidsecond group in the connection at the corresponding ones of said equallyspaced slots, and corresponding transfer gates in said paths of saidsecond group in the connection at corresponding ones of the randomlyselected time slots, whereby the information coupled to the input end ofone path of said second group of a connection for said second classequipment appears at the output end of the other path of the secondgroup in the connection in the same time slot one cycle thereafter.

References Cited by the Examiner UNITED STATES PATENTS Re. 24,679 8/1959Chubb et al. 179-189 2,546,935 3/1951 Trevor 179-15 2,564,419 8/1951Blown 179-15 2,754,367 7/1956 Levy 179-15 2,910,540 10/1959 Van Mierloet al. 179-189 2,917,583 12/1959 Burton 179-15 2,936,338 5/1960 James etal. 179-18.9 3,046,346 7/1962 Kramer 179--15.55

DAVID G. REDINBAUGH, Primary Examiner.

ROBERT H. ROSE, Examiner.

4. IN A COMMUNICATION SYSTEM HAVING A FIRST GROUP OF TRANSMISSION PATHSFOR TRANSMITTING SIGNALS WITHIN A FIRST PREDETERMINED BANDWIDTH, AND ATIME DIVISION SWITCHING NETWORK INCLUDING MEANS FOR ESTABLISHINGCONNECTIONS OVER SAID TRANSMISSION PATHS, THE PATHS IN DIFFERENTCONNECTIONS BEING ASSIGNED DIFFERENT TIME SLOTS OF A REPETITIVE CYCLEFOR TRANSMISSION PURPOSES, THE IMPROVEMENT WHICH COMPRISES: A SECONDGROUP OF TRANSMISSION PATHS, EACH PATH OF SAID SECOND GROUP INCLUDINGINPUT MEANS FOR RECEIVING SIGNALS HAVING A BANDWIDTH WHICH IS WIDER THANSAID FIRST BANDWIDTH, A PLURALITY OF SAMPLING MEANS OPERATIVE TO SAMPLESAID RECEIVED SIGNALS AT A PLURALITY OF DISTINCT EQUALLY SPACED TIMESLOTS OF EACH CYCLE, INCLUDING A PLURALITY OF